1. Field of the Invention
The present invention relates to a dry photographic copying method. More particularly, it relates to a dry photographic copying method wherein an image forming layer is image-wise exposed and contacted with an image receiving layer and then heated.
2. Description of the Prior Art
Methods for producing a copy by a dry photographic process are known. Among those is known a dry photographic process in which a colored image is formed on an image receiving sheet by image-wise exposing a light-sensitive layer containing a light-sensitive image forming compound which is changed to a non-transferable compound upon exposure and then contacting the light-sensitive layer with an image receiving layer and heating the light-sensitive layer to transfer the image forming compound to the image receiving layer. Necessary requirements for the above-described process are as follows. The image forming compound must lose transferability upon exposure, and an image forming component which can form a colored image upon reaction with the image forming compound must be contained in the image receiving layer; further, the image forming compound must be transferable upon heating, and the image forming compound and the image forming component must react when heated to form color.
One example of the above described process includes a light-sensitive layer containing a transferable compound and a sensitizing dye as described in U.S. Pat. Nos. 2,789,904 and 3,094,417. The transferable compound (e.g., 4-methoxy-1-naphthol) is converted to a non-transferable compound upon exposure. This compound is transferred from non-exposed areas of the light-sensitive layer to the image receiving layer by heating and reacts with a silver compound (silver behenate) to form a positive image.
A light sensitive layer containing an organic tellurium compound is described in Japanese Patent Publication (OPI) No. 29438/73. This compound is a compound in which a tellurium atom and an organic group are bonded directly [e.g., (C.sub.6 H.sub.5 COCH.sub.2).sub.2 -TeCl.sub.2 ], and a black image comprising free tellurium crystals is obtained when heating after image-wise exposing the above described organic tellurium compound containing light-sensitive layer in the presence of a proper optical sensitizing agent (e.g., benzophenone). Further, a complex formed from a tellurium halide and an organic base [e.g., (C.sub.14 H.sub.29 NH.sub.2)n : TeCl.sub.4, (CH.sub.3 COCoH.sub.4 --NH.sub.2).sub.2 : TeCl.sub.4, etc.] can also be used as a light-sensitive material like the above described compound, as is disclosed in Japanese Patent Publication (OPI) No. 14330/74.